Aqueous emulsion polymerization of ethylenic unsaturates in the presence of diazo-thio-ethers



Patented Mar. 28, 1950 AQUEOUS EMULSION POLYMERIZATI ON OF ETHYLENIC UNSATURATES IN THE PRES- ENCE OF DIAZO-IHIO-ETHERS William B. Reynolds andErnest W. Cotten, Cincinnati, Ohio, asslgnors to Phillips PetroleumCompany, a corporation oi Delaware No Drawing. Application January 17,1946,

Serial No. 641,866 1 This invention relates to the polymerization oiunsaturated organic compounds capable of undergoing an additionpolymerization to form high molecular weight polymers. In one of itsmore specific aspects itrelates to the polymerization of an aliphaticconjugated diene hydrocarbon, including substituted derivatives, eitheralone or in admixture with a monomer copolymerizable therewith, to formlong chain polymers of the type known as synthetic rubbers. In a stillmore specific aspect it relates to the polymerization of a butadiene-1,3hydrocarbon and a monomer copolymerizable therewith in an aqueousdispersion in the presence of an improved initiator for thepolymerization reaction. The present invention provides new compoundsuseful as initiators (catalysts) and modifiers for the polymerization ofunsaturated organic compounds either alone or in admixture with oneanother, and particularly in an aqueous dispersion, which compounds formtageously polymerized in accordance with the a present invention eitherin a homogeneous system or in the form of an aqueous emulsion. Suchunsaturated organic compounds are generally those which contain amethylene group attached b an olefinic double bond to a carbon atom inthe structure CH2=C Compounds which contain the CH2=C group and aresuitable as monomers for use in the process of our invention include thefollowing: butadiene-1,3; its homologues and analogues which polymerizein the same manner, e. g., isoprene, piperylene, chloroprene, etc.;styrene; acrylonitrile; methyl acrylate; methyl methacrylate; vinylchloride; etc. These unsaturated organic compounds are given by way ofexample only. The unsaturated or ganic compounds may be polymerizedalone or in admixture with other monomers copolymerizable therewith.

A number or unsaturated organic compounds 3 are capable of undergoingaddition polymerization reactions to form high molecular weight,

linear polymers known in the art as synthetic rubbers. Among the moreimportant synthetic rubbers at the present time are those which resultfrom the copolymerization of an aliphatic con- Jugated diene hydrocarbonand a monomer copolymerizable therewith in an aqueous emulsion. Thealiphatic conjugated diene hydrocarbons (or butadiene hydrocarbons)include butadiene-Lii. isoprene, dimethyl butadiene, piperylene, chloro-19 Claims. (01. zoo-84.3)

prene, and the like. Monomers copolymerizable with the aliphaticconjugated dienes in aqueous emulsionsystems include aryl olefins andsubstituted aryl olefins ,(e. g., styrene, p-chloro styrene, p-methoxystyrene, vinyl naphthalene, and the like); alkyl esters of'acrylic acids(e. g., methyl acrylate, methyl methacrylate, butyl acrylate, and thelike), nitriles of acrylic acids (e. g.,' acrylo nitrile,methacrylonitrile, and the like) vinylidine chloride, vinyl ketones (e.g., methyl vinyl ketone), vinyl ethers, vinyl carbazole, vinyl furan,

vinyl pyridine, and the like, all of which contain the CH2=C group.

An object of this invention is to provide a! improved process for theaddition polymerization Of unsaturated organic compounds to form highmolecular weight polymers. Another object is to provide an improvedprocess for the polymerization of aliphatic conjugated dienehydrocarbons. Another object is to provide an improved process for thecopolymerization of a butadiene hydrocarbon and a monomercopolymerizable therewith in an aqueous emulsion. Still another objectof this invention is to provide improved initiators or catalysts for usein polymerization reactions 01' this type. A further object or thisinvention is to provide compounds particularly suited as initiators andmodifiers in the emulsion polymerization of polymerizable organiccompounds. A still further object is to provide improved highmolecularweight polymers of unsaturated organic monomers. An important object ofthis invention is to provide an emulsion polymerization process in whicha novel initiator is employed to effect a reduction in the time requiredfor carry ing out polymerization reactions of this type.

In accordance with the present invention, polymerization of apolymerizable organic monomeric material, either alone or in admixturewith a monomer copolymerizable therewith, is carried out in the presenceof a diazo thin-ether. The polymerziation maybe carried out either in ahomogeneous system, as is more specifically disclosed and claimed incopending application Serial No. 8,735, filed February 16, 1948, or in aheterogeneous sytem, for example, in an aqueous dispersion or emulsion.It is preferred to carry out the polymerization in an aqueous emulsion.The term emulsion as used herein is to be construed in its broadestsense, that is, as denoting the presence of an aqueous phase and an oilphase without regard to the extent of dispersion 01' one in the other.In general, emulsion polymerization is carried out in an aqueousdispersion, i. e.. the monomers are dispersed in water, usually with theaid of a dispersing or emulsifying agent and agitation. Emulsifyingagents which are suitable for this purpose include partially orcompletely neutralized fatty acid soaps, sodium lauryl sulfate, sodiumisobutyl naphthalene sulfonate, sulfated and sulfonated succinic esters,and the like.

The diazo thio-ethers of the present invention have the generalstructural formula:

where R is a member of the group consisting of the aromatic andsubstituted aromatic radicals and R is a member of the group consistingof the aromatic, substituted aromatic, cycloalkyi, substitutedcycloaikyl, aliphatic, and substituted aliphatic radicals. These diazothio-ethers may be made by the combination of a diazotized aromaticamine and an aromatic, cycloaikyl or aliphatic mercaptan, includingsubstituted derivatives.

Examples of aromatic amines which may be used in the preparation ofdiazo thio-ethers are as follows: aniline, chloroaniline, bromoaniline,toluidine, anisidine, phenetidine, -aminodiphenyl ether, toluidine,dimethoxy aniline, nitroaniline, methyl-methoxy aniline, trimethylaniline, dichloroaniline, xylidine, chlorotoluidine, naphthylamine,dianisidine, benzidine, dicnlorobenzidine, sulfaniiic acid, aminobenzoicacid, toluidine sulfonic acid, naphthylamine sulfonic acid, andbenzidine disulfonic acid. Examples of mercaptans that may be used as acoupling component in the preparation of diazo thioethers are thefollowing: thio-phenol, thiocresol, chloro thio-phenol, methoxythio-phenol, thio-salicyciic acid, thio-phenol sulfonic acid,thio-naphthol, 2-mercapto3-naphthoic acid, thio-glycollic acid, ethylmercaptan, butyl mercaptan, t-butyl mercaptan, cyclohexyl mercaptan,mercapto benzothiazole, and octyl mercaptan.

The diazo thio-ethers preferred for use as polymerization catalysts inaccordance with the present invention are those in which both R and R inthe foregoing structural formula are aromatic or substituted aromaticgroups. Examples of preferred compounds are substituted phenyl diazothio-(naphthyl) ethers, phenyl diazo thio- (phenyl) ethers, naphthyldiazo thio-(phenyi) ethers, and naphthyl diazo thio-(naphthyi) ethers.Preferred substituent groups are the alkyl, alkoxy, aryloxy (e. g.,phenoxy), carboxy, sulfo (SOaH) halo, and nitro groups. Othersubstituents give diazo thio-ethers of varying degrees of usefulness.

The diazo thio-ethers can conveniently be prepared by diazotizing anaromatic amine and coupling the diazonium compound with an aliphatic oran aromatic mercaptan. Diazo thic- .ethers containing two diazothio-ether groupings can be prepared by tetrazotizing an aromaticdiamine and coupling the tetrazonium compound with two molecularequivalents of a mercaptan. The coupling to the mercaptan is usuallycarried out in a strongly alkaline medium although in some examples itis advantageousto carry out the coupling in weakly acidic media. Thecrude diazo thio-ethers isolated from the coupling are usually ofsumcient purity for use in polymerization reactions. However, if apurified product is desired the oil-soluble ypes may be purified bydissolving in acetone or anhydrous ether at about 10 0., cooling toabout -50 C. and filtering of! the recrystallized product. Thewatersoluble type diazo thio-ethers, in the form of their ammonium oralkali metal salw (resulting from coupling in an alkaline medium), canbe conveniently purified by washing with anhydrous ether.

New compounds prepared in accordance with this invention which arepreferred catalysts for the polymerization process of this invention arethose represented by the formula where Ar is an aryl group and X is asubstituent selected from the group consisting of alkyl, alkoxy, aryland aryloxy radicals, n is an integer from one to four, n being at leasttwo when a methyl radical is a substituent; and R is a member of thegroup consisting of aromatic, substituted aromatic, cycloalkyl,substituted cycloalkyl, aliphatic, and substituted aliphatic radi eais.When a methyl substituent is employed in the aryl group attached to thenitrogen at least one other methyl (or other alkyl), alkoxy, aryl, oraryloxy radical is also present. Specific examples of new compoundsforming a part of our invention are the following: p-methoxy phenyldiazo thio-(2-naphthyl) ether, dimethyl phenyl diazo thio-(2-naphthyl)ether, dimethyl phenyl diazo thio-(p-methoxy phenyl) ether, p-methoxyphenyl diazo thio-(o-carboxy' phenyl) ether, p-sulfo phenyl diazothio-(2-naphthyl) ether, p-sulfo phenyl diazo thio-(ptoly1) ether,2-naphthyl diazo thio-(carboxy phenyl) ether, and the like, togetherwith the ammonium and alkali metal salts of such compounds. Some of themore important new compounds may be conveniently represented by theformula x). where X is a substituent selected from the group consistingof alkoxy and aryloxy radicals. 11. is an integer from one to four, andR is a member of the group consisting of aromatic, substituted aromatic,cycloalkyl, substituted cycloalkyl, aliphatic, and substituted aliphaticradicals.

Conventional practice in emulsion polymerizations has been to addtogether a monomer or mixture of monomers capable of being polymerized,one or more of various initiators, catalysts, and modifiers, water andan emulsifying agent. The initiator used generally is either an organicperoxide or an inorganic peroxide material, usually used in combinationwith a modifying agent such as a mercaptan. In one commonly used systema water-soluble oxidant such as potassium persulfate is used inconjunction with an oil-soluble mercaptan which according to theory isoxidized, possibly in the aqueous or soap phase to a mercaptanfree-radical, which initiates polymer chain growth by combining with amonomer unit. There are certain inherent defects in such a chaininitiation system; and furthermore, the use of an oxidant such aspotassium persulfate may have certain undesirable features inasmuch asthe oxidant is likely to enter into certain undesirable side reactions.

We have now discovered that the defects of the above described system,which nevertheless is the best system previously known, can be largelyovercome through the use of diazo thioethers as polymerizationinitiators. Furthermore the diazo thio-ethers have the great advantageof functioning also as modifiers of chain growth, thus making itpossible to control the molecular weight and properties of the polymerwithout the use of additional modifiers. However. it is sometimesadvantageous to use supplementary modifiers in addition to the diazothioether.

Although the exact mechanism of chain initiationby diazo ,thio-ethers isnot known it is possible thatthe chains are initiated by free radicalsformed by decomposition of the diazo thio-ether. Free radicals can beformed, for example, according to the following reaction:

Either or both of the above free radicals might then initiate polymerchain growth by reacting with a monomer unit according to reactions suchas the following:

According to this mechanism the free radicals R- and R'S may then reactwith new monomer thus initiating new polymer chains.

The theory set forth aboveis a possible explanation of the mechanisminvolved in the function of diazo thio-ethers of our invention inemulsion polymerization reactions. This theory is included herein onlyas an aid in understanding the present invention and is not to beconstrued as in any way limiting the invention. Regardless of themechanism postulated, the fact remains that the diazo thio-etherseffectively catalyze and modify emulsion polymerization reactions.

One of the greatest advantages of the use of diazo thio-ethers inpolymerization reactions in r accordance with our invention is theirgreat versatility. Diazo thio-ethers of almost any desired reactivitycan be prepared by suitably varying the radicals R. and R. For example,if R and R are both aromatic radicals, diazo thio-ethers of greatactivity can be obtained if either or both of the radicals containactivating substituents, for example, alkyl or alkoxy groups. Iflowactivity initiators are desired for polymerization reactions athigher temperatures the radicals R and R can contain deactivatingsubstituents, for example, chloro or nitro groupings. When R. isaliphatic, diazo thio-ethers of high activity are obtained. Considerablevariation in this high activitycan be obtained by varying thesubstituents on the aromatic radical R.

The diazo'thio-ethers are still more versatile as polymerizationpromoters since they may be oil soluble or water soluble as desired. Inorder to prepare water soluble diazo thio-ethers it is only necessarythat either or both of the radicals R or R contain a water' solubilizingsubstituent, for example, the carboxylic or sulfonic acid 4 merizationreaction in order to provide more uniform modification and to obtainmore eflicient groups or other hydrophilic groups. Such water solublediazo thio-ethers are conveniently pre- 6 pared and used in the form oftheir ammonium or alkali metal salts. In general the initiator activityvor the water soluble diazo thio-ethers may be said to be somewhatgreater than that of comparable oil soluble diazo thio-ethers. However,both types appear to be of similar emcienc'y as polymerizationmodifiers.

The type and amount of diazo thio-ether usedin a particularpolymerization recipe depends upon the result desired. Forpolymerizations to be carried out at low temperatures (e. g., 10 to 40C.) an active diazo thio-ether is chosen. The water soluble types areparticularly satisfactory for low-tempertaure recipes. In carrying outpolymerization in an aqueous emulsion at a temperature below thefreezing point of the aqueous phase, an inert freezing point depressantis em'-' ployed. For polymerizations to be carried out at" highertemperatures (e. g., 40-60 C.) diazo thiti j ethers of moderate activityare chosen while for even higher temperature polymerizations diazothio-ethers of low activity are selected. In general, approximately 0.2part by weight of the' diazo thio-ether, based on the weight of themonomeric material, will give satisfactory promotion although otherproportions within the' range of about 0.05 to about 5.0 parts byweight, based on 100 parts by weight of the monomeric material, may beused. The diazo thio-ether may be added in increments throughout thepolyutllization of the diazo thio-ether. If the diazo thio'ether is usedalone to modify the molecular weight of the polymer somewhat largerquantitles are needed than is the case it other modifiers are used inconjunction therewith. It is often desirable to add an auxiliarymodifier such as a dodecyl mercaptan to the polymerization recipe.

Typical examples of our invention are the following:

Example I 123 parts of p-anisidine are. dissolved in 3,000 parts ofwater with 91 parts of hydrogen chloride (100%) used as a 36% solution.The resulting solution is cooled to 0 to 5 C. and diazotized by theaddition of parts of sodium nitrite dissolved in 200 parts of water. Thediazonium solution is poured rapidly into a solution of 163 parts ofthio-beta-naphthol and 400 parts of sodium hydroxide in 4,500 parts ofwater at 0 to 5 C. The diazo thio-ether, p-methoxy phenyl diazothio-(z-naphthyl) ether, immediately precipi tates as a finely dispersedoil, which soon-solidifies to a yellow solid. The solid material isfiltered ofi, washed thoroughly, and dried at room temperature undervacuum. This thio-ether is oil soluble.

Two parts of the diazo thio-ether are added to an agitated autoclavecontaining water 180 parts, soap 5 parts, butadiene parts, and styrene25 parts. Agitation is continued for nine hours while the chargetemperature is maintained at 50 C. by means of water circulation in theautoclave jacket. At the end of nine hours the charge is discharged intoa stripping tank where the unreacted monomers are recovered by steamdistillation. The latex is creamed by the addition of a small amount ofsodium chloride solution and coagulated by the addition of dilutesulfuric acid. The rubber crumb is washed sev. eral times by decantationand, finally, dried in a-vacu'um oven at 60 C. The product, which isthus obtained in about 80% conversion based upon the weight of startingmonomers, is a soft. well-modified rubber which is soluble in benzeneand has good properties when compounded and vulcanized in conventionalways.

Example I! 145 parts of beta-naphthylamine are diazotized in 2,000 partsof water containing 250 parts of 10 N hydrochloric acid by the additionof a solution of 70 parts of sodium nitrite. The resulting diazoniumsolution is run slowly into a solution of 162 parts of thio-salicylicacid in 10,000 parts of water containing 80 parts of sodium hydroxideand 410 parts of sodium carbonate. The sodium salt of beta-naphthyldiazo thio-salicylic acid precipitates and is filtered and washedthoroughly with 10% sodium sulfate solution and, finally, once with asmall amount of cold water. The product, 2-naphthy1 diazo thio-(carboxyphenyl) ether, is dried at room temperature under vacuum. Ii desired itcan be purified by washing with a little anhydrous ethyl ether. Theresulting product is of the water soluble type.

When used in a polymerization recipe essencomparable to those of ExampleI.

Example III 173 parts of sulfanilic acid are diazotizes in 2,000 partsof water containing 25 parts of 10 N hydrochloric acid by the additionof a solution of 70 parts of sodium nitrite. The cold diazonlum solutionis poured rapidly into a cold solution of 131 parts of p-thio-cresol in5,000 parts oi water containing 80 parts of sodium hydroxide and 82parts of sodium acetate. The bright, yellow sodium salt of the diazothio-ether precipitates immediately and is isolated, washed, and driedas in Example II. This product, p-sulio phenyl diazo thio-(p-tolyl)ether, is of the water soluble type.

One part of the diazo thio-ether is added to a polymerization mixturecontaining 180 parts of water, 5 parts of Aerosol AY (a commercial,synthetic detergent described as a succinic ester suli'onate), 75 partsof butadiene, and 25 parts of styrene. Polymerization is carried out atC. for 12 hours and the rubber isolated by methods analogous to those ofExample 1.

Example IV Two parts of the diazo thio-ether prepared by couplingdiazotized p-anisidlne with thio-salicylic acid, p-methoxy phenyl diazothio-(carboxy phenyl) ether, (a diazo thio-ether of the water solubletype), are added to a polymerization recipe containing 180 parts ofwater, 5 parts of Aerosol AY, 75 parts of butadiene, and 25 parts ofstyrene. Polymerization is carried out at 25 C. for twelve hours and theproduct isolated as in Example I. A well modified rubber of goodproperties is obtained.

Example V 0.3 part of the diazo thio-ether of Example I is added to apolymerization recipe containing 180 parts of water, 5 parts of soap,0.4 part of dodecyl mercaptan, '75 parts of butadiene and 25 parts 01'styrene. Polymerization is continued for 12 hours at 50 C. and theproduct isolated as in Example I. A well modified rubber of goodproperties is obtained.

is obtained.

Example V1 0.3 part of the diazo thio-ether oi llllxainplef is added toa polymerization recipe containingm80 parts of water, 5 parts of soap,0.2 part of potassium persuliate, 0.4 part of tertiary dodecylmercaptan, 75 parts of butadiene, and 25 parts of styrene.Polymerization is continued for 10 hours and the rubber isolated as inExample 1.

Example VII An autoclave is charged exactly as in Example I except thatisoprene is used in place of the butadiene. A comparable rubber of verygood properties is obtained.

Example VIII Two parts of the diazo thio-ether of Example I ,are addedto a polymerization mixture of water 180 parts, soap 5 parts, butadiene75 parts and methyl methacrylate 25 parts. Polymerization proceedsrapidly at 50 C. to give an elastom'er having certain very desirableproperties.

Example IX One part of the diazo thin-ether of Example I is added toparts of ethyl acrylate. The solution is run slowly into an agitatedautoclave containing parts of water and one part of Aerosol AY, thebatch temperature being maintained at 50 C. An acrylic polymer ofvaluable properties Example X Example XI Two parts oi. the diazothio-ether of Example I are added to a polymerization recipe of parts ofwater, 5 parts of soap, 70 parts of butadiene and 30 parts ofacrylonitrile. Polymerization is carried out at 50 C. and the productisolated in Example I.

1 Example XII A polymerization is carried out exactly as in Example Iexcept that vinyl pyridine is used in place of styrene. A well modifiedrubber of good properties is obtained.

Example XIII A polymerization is carried out exactly as in Example Iexcept that dichlorostyrene is used in place of styrene. A well modifiedrubber of good properties is obtained.

Example XIV Two parts of the diazo thio-ether prepared in Example I areadded to a polymerization mixture consisting of 180 parts of water, 5parts of dodecyl amonium acetate, 75 parts of butadiene and 25 parts ofstyrene. Polymerization is carried out at 40 C. The stripped latex iscoagulated, isolated and dried in the usual way.

Example XV 0.5 part of the diazo thin-ether, dimethyl phenyl diazothio(2-naphthyl) ether, prepared by coupling diazotized m-xylidine withthio-betanaphthol is added to a polymerization mixture containing 180parts of water, 5 parts of soap, 75 parts oi butadiene and 25 parts orstyrene.

. 9 v Polymerization is carried out at 50 C. for 3 hours to obtain a 65%conversion of a soft, well-modifled rubber of good properties. When thediazo thio-ether was replaced by 0.3 part of potassium persulfate and0.5 part of dodecyl mercaptan in the above recipe, ten hours wererequired to effect the same amount of conversion.

Example XVI The polymerization of Example I was carried out in which atotal of 0.75 part of the diazo thio-ether was added in increments asthe polymerization proceeded. 05 part of the promoter was added at'thebeginning of the reaction, 0.3 part was added at the end of one hour and0.4 part was added at the end of four hours. Polymerization conversionwas in seven hours at 50 C. The rubber wascompletely soluble in benzeneand had very go d properties. crement manner of addition was found todecrease materially the proportion of diazo thioether required whileproviding uniform modifyin'g action.

The foregoing examples illustrate preferred methods of practicing thisinvention and are to be construed as being illustrative only, without inany way limiting the scope of the invention.-

An important advantage of the process of this invention and thecatalysts employed therewith is illustrated in the examples illustratingthe use or diazo thio-ethers of both the oil-soluble and thewater-soluble types. The choice of the diazo thio-ether also affects therate of polymerization as is illustrated in the examples. Catalysts ofour invention may be employed to effect very rapid polymerization of themonomeric materials. if desired, and make possible continuous emulsionpolymerization in lieu of the conventional batch process. Anotherimportant advantage of the process of this invention and the catalystsemployed therein is that emulsion polymerization may be carried outusing recipes containing less soap than is necessary for conventionalemulsion polymerization. This results in a polymer of low residual soapcontent and of improved quality (for certain uses).

The rubbers produced by the methods of the present invention are foundto have excellent properties when evaluated in comparison with standardsynthetic rubbers in conventional compounding recipes. Standard treadstocks prepared from polymers made in accordance with the presentinvention have room temperature tensile strengths in the range of 3000to 3500 pounds per square inch or more and room temperature elongationsin the range of 600 to 800 per cent or more. Other properties such ashysteresis, flex life, abrasion resistance, etc., of the products of thepresent invention in many cases possess definite superiority overpolymers produced by conventional methods.

Although we have disclosed specific embodiments of our invention. itwill be apparent that the initiators and polymerization process of ourinvention are capable of broad application in the art, and that variousmodifications may be made without departing from the scope of theinvention.

We claim:

1. In a process of polymerizing by addition polymerization anethylenically unsaturated polymerizable organic compound to form a highmolecular weight linear polymer, the step which comprises polymerizingsaid unsaturated organic This in-.

10 compound in aqueous dispersion in the presence of a diazo thio-etherof the formula where R is a member of the class consisting of aromaticradicals, and R is a member of the class consisting of aromatic,cycloalkyl. and aliphatic radicals.

2. The process of claim 1 wherein said polymerization is effected in.the presence of 0.05 to 5 parts by weight. based on parts by weight ofsaid unsaturated organic compound, of such a diazo thin-ether.

3. The processor claim 1 wherein a diazo thioether is added at the startof said polymerization and also at least once during the course of thepolymerization reaction.

4. The method which comprises polymerizing in aqueous dispersion apolymerizable unsaturated monomeric material comprising an allphaticconjugated diene containing a CH2==C group and which undergoes anaddition polymerization to form a high molecular weight linear polymerin the presence of a diazo thin-ether o! the formula R-N=NS-R' where Ris a member of the class consisting of aromatic radicals, and R. is amember of the class consisting of aromatic, cyclo-alkyl, and aliphaticradicals.

5. The method which comprises copolymerizing in an aqueous dispersion aconjugated diene hydrocarbon and an organic ethylenically unsaturatedmonomer copolymerizable therewith in an aqueous dispersion in thepresence of a diazo thio-ether of the formula RN=N-S-R' where R is amember of the class consisting of aromatic radicals and R is a member ofthe class consisting of aromatic, cyclo-alkyl, and aliphatic radicals.

6. The method which comprises copolymerizing in an aqueous dispersionbutadiene-1,3 and an organic ethylenically unsaturated monomercopoLvmerizable therewith in an aqueous dispersion in the presence of adiazo thio-ether of the formula R-N=NS--R' where R is a member of theclass consisting of aromatic radicals and R is a member of the classconsisting of aromatic, cyclo-alkyl, and aliphatic radicals.

7'. The method which comprises polymerizing a hydrocarbon monomericmaterial comprising a major portion of butadiene-1,3, and a vinylaromatic hydrocarbon in an aqueous dispersion in the presence of 0.05 to5.0 parts by weight on the basis of the monomers of a diazo thio-etherof the formula R-N=NSR' where R is a member of the class consisting ofaromatic radicals and R. is a member of the class consisting ofaromatic, cyclo-alkyl', and aliphatic radicals.

8. The method which comprises copolymerizing in an aqueous emulsionbutadiene-l,3 with an organic ethylenically unsaturated monomercopolymerizable therewith in an aqueous emulsion in the presence ofp-methoxy phenyl diazo thio-(z-napthyl) ether.

9. The method as defined in claim 8 wherein said comonomer is styrene.

10. The method which comprises copolymerizing in an aqueous emulsionbutadiene-1,3 with an organic ethylenically unsaturated monomercopolymerizable therewith in an aqueous emulsion in the presence ofdimethyl phenyl diazo thio-(z-naphthyl) ether. V

11. The method which comprises copolymerizing in an aqueous emulsionbutadiene-1,3 with an organic ethylenically unsaturated monomercopolymerizable therewith in an aqueous emul- 11 sion in the presence ofp-methoxy phenyl diam thio-(carboxy phenyl) ether.

12. The process of making a polymeric synthetic rubber, which comprisescopolymerizing in aqueous emulsion at a polymerization temperaturebetween -10 and 60 C. a liquid monomeric material comprising a majorportion of butadiene-1,3 and a minor portion of styrene in the presenceof 0.05 to '5 parts by weight, based on 100 parts by weight oi saidmonomeric material, oi p-methoxy phenyl diazo thio-(2-naphthyl) ether,and recovering a resulting polymeric synthetic rubber so produced.

13. The process 01' making a polymeric synthetic rubber, which comprisescopolymerizing in aqueous emulsion at a polymerization temperaturebetween -10 and 60 C. a liquid monomeric material comprising a majorportion of a butadiene-1,3 and a minor portion an organic ethylenicallyunsaturated monomer copolymerizable therewith in aqueous emulsion in thepresence of 0.05 to 5 parts by weight, based on 100 parts by weight oisaid monomeric material, of p-methoxy phenyl diazo-thio-(Z-naphthyl)ether, and recovering a resulting polymeric synthetic rubber soproduced.

14. The process of making a polymeric synthetic rubber, which comprisescopolymerizing in aqueous emulsion at a polymerization temperature aliquid monomeric material comprising a butadiene-1,3 in the presence of0.05 to 5 parts by weight, based on 100 parts by weight of saidmonomeric material, of p-methoxy phenyl diazo thio-(Z-naphthyl) ether,and recovering a resulting P lymeric synthetic rubber so produced.

15. In a process of polymerizing in aqueous emulsion a liquid monomericmixture containing butadiene-1,3 and styrene, the step which comprisesadding p-methoxy phenyl diazo thio-(2- naphthyl) ether to the monomericmixture before polymerization and subsequently effecting acopolymerization 01' said butadiene-1,3 and styrene.

16. The process of making a polymeric synthetic rubber, which comprisescopolymerizing in aqueous emulsion at a polymerization temperaturebetween and 60 C. a liquid monomeric material comprising a major portionof butadiene-1,3 and a minor portion of styrene in the 12 presence of0.05 to 5 parts by weight, based on 100 parts by weight or saidmonomeric material, 01' a p-methoxy phenyl diazo tine-(naphthyl) ether,and recovering a resulting polymeric s thetic rubber so produced.

17. The process of making a polymeric synthetic rubber, which comprisescopolymerizing in aqueous emulsion at a polymerization temperaturebetween -10 and C. a liquid monomeric material comprising a majorportion of butadiene-1,3 and a minor portion of styrene in the presenceof 0.05 to 5 parts by weight, based on parts by weight of said monomericmaterial. of a phenyl diazo thio-(aryl) ether, and recovering aresulting polymeric synthetic rubber so produced.

18. In a process of emulsion polymerizing an aliphatic conjugated dienein aqueous emulsion, the step of conducting said polymerization in thepresence of p-methoxy phenyl diazo thio-(2- naphthyl) ether in an amountbetween 0.05 and 5 parts by weight, based on 100 parts of said monomericmaterial.

19'. In a process of emulsion polymerizing an aliphatic conjugated dienein aqueous emulsion, the step of conducting said polymerization in thepresence of a diazo thio-ether in an amount between 0.05 and 5 parts byweight, based on 100 parts of said monomeric material, said diazothin-ether having the formula RN=N-SR' where R is an aromatic radicaland R is an organic radical selected from the groupconsisting ofaromatic cycloalkyl, and aliphatic radicals.

WILLIAM B. REYNOLDS. ERNEST W. CO'I'IEN.

REFERENCES CITED The following references are of record in the file ofthis patent:

UNITED STATES PATENTS Number Name Date 1,975,409 Schnitzspan Oct. 2,1934 2,251,156 Nygard July 29, 1941 2,313,233 Fryling Mar. 9, 19432,376,963 Garvey May 29, 1945 2,380,473 Stewart July 31, 1945

1. IN A PROCESS OF POLYMERIZING BY ADDITION POLYMERIZTION ANETHYLENICALLY UNSATURATED POLYMERIZABLE ORGANIC COMPOUND TO FORM A HIGHMOLECULAR WEIGHT LINEAR POLYMER, THE STEP WHICH COMPRISES POLYMERIZINGSAID UNSATURATED ORGANIC COMPOUND IN AQUEOUS DISPERSION IN THE PRESENCEOF A DIAZO THIO-ETHER OF THE FORMULA.